The goal of this proposal is to achieve an increased understanding by means of a detailed clinical study of sudden hearing loss (SHL), a relatively common disorder with an attack rate of about 15/100,000 population per year. This syndrome affects all ages and sexes, and its principle causes probably include viral infections, cochlear membrane rupture, and vascular occlusion. Our objectives will include a continuation of an ongoing prospective clinical study at Massachusetts Eye and Ear infirmary which currently attracts 30-35 new patients annually. However, we would extend our patient sample through collaboration with Dr. Frederick Byl at the Kaiser-Permanent Group referral center in Oakland, CA and Dr. Phillip Sprinkle, West Virginia Univeristy, Morgantown. The prospective clinical study planned in this proposal will assess the relationship of idiopathic (I)SHL to seasonal, genetic, environmental as well as occupational factors by use of a thorough patient history obtained on a standardized questionnaire. By means of medical examination to include an otologic evaluation, audiogram, ENG, x-ray, routine laboratory studies, and when possible, electrocochleography; we hope to assess the role of underlying medical conditions such as viral infections, diabetes and previous ear disease in ISHL. Also, these procedures will aid in our further classification of the causes of ISHL. Another objective is the serological evaluation of paired sera obtained from 45 patients is banked at -70 degrees C in preparation for analysis. Finally, we will continue an ongoing double-blind clinical study of a potentially beneficial treatment that includes steroids and placebo. Currently 65 patients are enrolled in Oakland and Boston. All data generated from the above studies is entered on a standardized data form for statistical analysis at the Health Sciences Computing Facility, School of Public Health, Harvard University. The result of such an inter-institutional collaborative clinical and laboratory study will be a better understanding of the etiology, classification, and treatment of ISHL.